They are believed to be the first Iraqis to have surrendered, something the American Air Force has been actively encouraging by dropping more than 1 million leaflets in anticipation of a ground invasion.

The soldiers — not technically prisoners of war, since the war has not yet started — are in the custody of the Kuwaiti border police, said Capt. Darrin E. Theriault, commander of the headquarters company of the division's First Brigade.

The development was welcomed by troops here making the final preparations for an attack that could begin at any moment, some of whom whooped with relief when the word trickled through the brigade's new headquarters in northwestern Kuwait.

The surrender came as a blinding desert sandstorm enveloped American and British armies struggling to wheel into final position on the Iraqi frontier to await the order to wage a war intended to topple Saddam Hussein's government in Baghdad.

Across 5,000 square miles of Kuwaiti desert, the wind whipped up a huge yellow nimbus of dust and sand that raked the convoys of tanks, troop transports and huddled infantry after a night in which artillery fire echoed through the border region near southern Iraq. But the sandstorm did little to slow the mass movement across the Kuwaiti desert. Commanders reported only routine breakdowns and no accidents.

Military officials said a series of naval clashes around the Iraqi port of Basra during the night were the result of an attempt by Iraqi military forces to send a small armada of wooden fishing vessels into the Persian Gulf, where American commanders feared they could be used in suicide strikes on allied warships assembled there.

As the hours counted down on President Bush's 48-hour ultimatum for Mr. Hussein to go into exile or face war, United States Army and Marine divisions rolled into new formations and there was an expectation that air and ground combat operations could start promptly after the deadline expired here at 4 a.m. Thursday (8 p.m. today, Eastern time), if not sooner. Today President Bush met in Washington with foreign policy advisers to review military plans.

Army and marine commanders have drawn up extensive plans to deal with hundreds, perhaps thousands of prisoners as the war begins.

"We anticipate more as this continues to develop," Captain Theriault said.

As troops moved into attack positions, soldiers donned their Kevlar helmets and vests. The brigade also distributed more ammunition, both for rifles and heavier weapons, like grenade launchers.

"There's a heightened sense of anticipation," said Col. William F. Grimsley, the brigade's commander. "The trick is to not let it become overwhelming."

By this evening, the Third Infantry Division's heaviest firepower had moved into place on the frontier, churning up swirling plumes of dust and sand as large columns of tanks, armored vehicles and other weapons left one threadbare desert camp for another even more desolate.

With the division's troops now in assault positions, commanders reported few signs of defensive preparations by Iraq's border troops — something that seemed to be confirmed by the surrender this evening.

"Surprisingly," Colonel Grimsley said, "we have seen very little over there since the president's speech."

The 130,000-member mechanized army in Kuwait formed a broad arc of thousands of vehicles, shoulder to shoulder in a sprawling phalanx facing north and visible to journalists scouting the area.

In the front of the formations, engineering battalions wheeled their bulldozers and heavy equipment into position to breach the ditches and earthen berms that lay between the army and the Iraqi desert.

Army meteorologists were confident that the weather would clear this evening and that the allied armed forces over the next three days would operate under clear skies with cool temperatures and minimal winds.

Still, in airborne units that rely heavily on helicopter gunships and transports, final training exercises were canceled today.

Helicopter assaults are a crucial part of the initial war plan, military officials said, as airborne forces are set to seize and protect Iraq's oil fields, establish forward supply and air assault bases inside Iraq and knock out critical air defense sites and suspected chemical weapons depots that could threaten advancing forces.

Artillery fire echoed through the Iraqi border region on Tuesday night and Iran's state television showed video of explosions from airstrikes in and around the Iraqi port of Basra.

A full March moon illuminated an army of 130,000 American and British soldiers arrayed with a host of M1A1 Abrams tanks, armored vehicles of every description, ubiquitous Humvees and humble troop transports, many of them short of equipment spares and tires as quartermasters scrambled to catch up.

In the front of the formations, engineering battalions wheeled their bulldozers and heavy equipment into position to breach the ditches and earthen berms that lay between the army and the Iraqi desert.

The sky over northern Kuwait was so thick with assault and transport helicopters on Tuesday that meteorologists trying to track the advancing sandstorm were forbidden to launch their weather balloons. Hundreds of helicopter pilots engaged in last-minute training exercises to master blind descents through the clouds of sand kicked up by their rotors.

Less visibly, military officials said American Special Operations forces had deployed from their bases on secret missions into Iraq, signaling that the invasion was imminent.

Out in the Persian Gulf, the commander of American and British naval forces, Rear Adm. John M. Kelly, expressed concern that Iraq was preparing attacks on coalition warships.

On Monday night, Iraqi Army troops sent a large number of fishing vessels from coastal ports and moorings and sent them into waters where aircraft carriers, destroyers and submarines were standing by to launch aircraft and cruise missiles against targets in Iraq. Military intelligence monitoring also detected the preparation of missile launching sites that could be directed at naval targets, he said.

Admiral Kelly said, "Our concern now" was that the Iraqi leaders "may be more inclined to act" against allied warships. Speaking aboard the carrier Abraham Lincoln, he added, "The game could begin at any time."

Elsewhere on land, there were signs of supply shortages and bottlenecks.

"I am not bringing my company into the desert without spare tires for every Humvee, because I know we are going to have flats," one exasperated Army major said. He worried himself through the day over the "breakdown issue" that he said was looming because of shortages of equipment needed to support the Army on its 300-mile trek to Baghdad.

At the 101st Airborne encampment, armed guards were stationed to prevent pilfering from trucks loaded with drinking water supplies. Hundreds of soldiers were still lining up at Army V Corps headquarters, trying to get last-minute anthrax and smallpox vaccinations.

C-130 aircraft packed with radio transmitters flew lazy circles over the Persian Gulf broadcasting messages in Arabic to the Iraqi people that were monitored by reporters near the border.

"We are fighting for a just cause to liberate a persecuted people, and to guarantee the American people's security," the broadcast said. "The soldiers of the United States will carry out their mission with honor and bravery."

In a reference apparently intended to assure Shiite Muslims who predominate in southern Iraq, the American broadcast said, "Every segment of the Iraqi population will be represented in the government" that Washington would help to form as an eventual successor to the 23-year rule of Mr. Hussein.